Some internal combustion engines utilize a compression device such as a turbocharger to increase engine torque/power output density. In one example, a turbocharger may include a compressor and a turbine connected by a drive shaft, where the turbine is coupled to an exhaust manifold side and the compressor is coupled to an intake manifold side of an engine. In this way, the exhaust-driven turbine supplies energy to the compressor to increase the pressure (e.g. boost, or boost pressure) in the intake manifold and to increase the flow of air into the engine. The boost may be controlled by adjusting the amount of gas reaching the turbine, for example with a wastegate. An actuator may be operatively coupled via a linkage to a wastegate valve and driven to position the wastegate valve to achieve the desired boost based on operating conditions. The actuator may be an electric actuator such as a motor with speed reduction gears, for example. A position sensor may provide feedback indicating the location of the wastegate valve relative to a valve seat. Depending on its location, the linkage may be subjected to significantly large forces, vibration, and temperatures.
In some approaches, a wastegate valve is located in a turbine housing with a wastegate arm extending outside the housing for controlling the wastegate. An actuator may be mounted a distance away from the turbine housing in order to avoid overheating the actuator. A linkage connects the actuator to the wastegate arm.
The inventors herein have recognized a problem with such approaches. In particular, linkages may deflect (e.g., bend) when subject to relatively high forces (e.g., actuator and/or exhaust forces). Linkage deflection may result in inaccurate wastegate valve positioning and thus inaccurate boost control.
Methods for compensating a deflected linkage in a wastegate arrangement are provided.
In one example, current is applied to an actuator to move a wastegate valve coupled through a linkage to the actuator for diverting gasses from a turbocharger. The position of the actuator is indicated, and a correction to said indicated actuator position is applied compensating for deflection of the linkage based at least on the applied current. The applied current is adjusted when the corrected actuator position reaches a position corresponding to a desired valve position.
In a more specific example, a correction for deflection of the linkage is retrieved from a stored data base created during previous test cycles and based on the applied current and temperature of the linkage.
In another aspect of the example, the correction was created using a test procedure comprising: increasing the applied current to move the valve to a fully closed position; after the valve is held in the closed position, further incrementing the applied current to cause deflection in the linkage, wherein a change in the indicated actuator position during the applied current incrementing step is stored as the correction for the deflection.
In still another example, the correction was created using a test procedure comprising: determining a fully closed position of the valve; when the valve is subsequently in an open position, issuing a closing command current to the actuator; inferring the actuator position based on the closing command current and the determined fully closed position; and creating the position correction based upon a difference between the inferred actuator position and the indicated actuator position.
In the examples described above, linkage deflection which would otherwise result in inaccurate wastegate valve positioning is compensated. Currents applied to an actuator may be controlled to move the actuator to a corrected position based on determined position corrections. Thus, the technical result is achieved by these actions.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.